Party-line revertive ringing system



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, 1,450,321 A.,E'. LUNDELL ET AL PARTY LINE REVERTIVE RINGING SYSTEMgli? mma June leso by Mx l pr. 3, 1923.

1,450,321 A. E. LUNDELL ET AL PARTY LINE REVERTIVE RINGING SYSTEM FiledJune 4, 1920 '7 sheets-sheet 2 /H sua/fors fq/ben f. L unda/l Apr. 3,1923.

A. E. LUNDELL ET AL PARTY LINE REVERTIVE-RINGING SYSTEM Filed June 4,1920 '7 sheets-sheet 5 Apr. 3, 1923. 1,450,321

A. E. LUNDELL ET AL PARTY LINE REVERTIVE RINGING SYSTEM /ben EL Lande/lfo/'7e Thompson 'by my.

A. E. LUNDELL ET AL PARTY LINE REVERTIVE RINGING SYSTEM Fll'ed June 4,1920 '7`sheets-sheet 5 Apr. 3, 1923. 1,450,321

A. E. LUNDELI. ET AL PARTY LINE REVERTIVE RINGING SYSTEM Filed June 4,1920 '7 sheets-sheet 6 Patented pr. 3, 1923.

UNHTED STATES insana rsrsnr carica.

ALBEN E. LUNDELL, OF CHICAGO, ILLINOIS, .AND GEORGE THOMPSON, OF MOUNTVERNON, NEW YORK, ASSIGNORS TO WESTERN ELECTRIC COMPANY, INCORPO- RATED,OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

PARTY-LINE REVERTIVE RINGING SYSTEM.

Application led .Tune 4,

T o all 'whom 'it cna-y concern Be it known that we, ALBEN E. LUNDELLand (l1-:Ouen THOMrsoN, citizens of the United States, residing atChicago, in the 5 county of Cook. State of Illinois, and at MountVernon, in the county of Westchester, State of New York, respectively,have invented certain new and useful Improvements in Part -LineRevertive Ringing Systems` of which the'following is a full,

clear` concise, and exact description.

This invention relates to automatic telephone exchange systems and moreparticularly to full mechanical systems of large capacity.

It is the object of this invention to provlde an improved revertiveringing system.

A feature of the invention is an arrangement whereby a callingsubscriberl may, under the control of his impulse sending device`establish conditions such that he may signal a subscriber on his ownparty linel without the necessity of obtaining the assistance of anoperator.

A further feature of the invention is the provision of an organizationsuch that no selective switches need be positioned in order toaccomplish the desired ringing operations` it being merely necessary forthe calling subscriber to establish connection to a register sender.

In order to accomplish revertive ringing Ou a party line it has usuallybeen necessary to provide special apparatus at the calling substationsso that extra manipulations by the calling subscriber are relluired. orelse it has been necessary for him to set numerical switches toestablish a connection to an operator who then instructs him to replacehis receiver, whereupon the desired ringing current is supplied underthe control of such operator. An additional scheme which is sometimesused is one wherein certain of the numerical selector switches areprovided with a special group of contacts to which ringing generators ofvarying characteristics are connected, and if these numerical switchesare then directively positioned,v the proper ringing current is thensupplied to the party line.

The present system provides many advantages over any of the abovearrangements. The operation of the system in general is as follows.Since the invention has been 1920. Serial No. 386,517.

' call is to be made, the oflice designation to be dialed is always thesame, regardless of what office the party line appears in, and eachsubscriber on each party line is provided with a list of the names ofthe subscribers whose stations appear on his line. The numbers andoffice designations which are given to him individually will, of course,be different from the numbers and office designations which appear inthe regular directory.

The subscriber upon initiating a call will seize an idle trunk leadingto a numerical switch which normally controls the selection of a desiredolice. A register sender is then automatically associated with his lineand he will dial in the usual manner and position a set of registeringdevices. If hefirst dials the code which has been taken for use inconnection with revertive calls, theregisters which normally controltheselection of the desired oiiice will be positioned in sucha way that noselections take place but instead ringing apparatus will be connected tothe calling line. As soon as the calling subscriber replaces hisreceiver, which he will be instructed to do when initiating a call whichis to be revertive on his own line, this ringing apparatus is put intooperation and will alternately signal the substation of the calledsubscriber and theV substation of the subscriber who initiated the call.The selection of the proper kinds of ringing current will be controlledby the numerical registers which would normally operate to control thenumerical switches to select the desired line in the selected oliice.

A complete understanding ofthe invenshows the circuits of a districtselector switch and a sender selector switch. 3 shows registercontrolling equipment and an associated sequence switch. Fig. 4 showsthe ringing apparatus. The sequence switch contacts shown at the rightof Fi are controlled by the sequence switch o Fig. 3. Figs. 5 and 6 showthe registerlng devices and the various contacts controlled by them, thecontacts controlled by each register appearing verticallyl above suchregister in Figs. 5 and 6. Fig. ,7 shows the counting relay sendingdevice with lts associated ste ping relay and controlling sequence switcThe operation of the system when a nonrevertive call is put through willfirst be described.

The subscriber at substation 1 desiring to initiate a call will .removehis receiver from the switch-hook, whereupon a circuit is completed fromgrounded battery, left-hand winding of line relay 2, upper middlearmature and back contact of cut-off relay 3, conductor 4, through theapparatus at the substation, conductor 5, the outermost upper armatureand back contact of cut-off relay 3, right-hand winding of line relay 2to ground. Relay 2 is energized in this circuit and completes a circuitfrom grounded battery, resistance 6, armature and back contact ofstepping magnet 7, armature and front contact of line relay 2, conductor9, normal contact 10 and its associated brush 11, and the winding Aofstepping ma et 7 to ground. Magnet 7 is energized in t is circuit andadvances the line switch Wipers one step. As soon as the line switchwipers engage thc second set of terminals in the arc served by them, .aself interrupting circuit is completed for stepping magnet 7, thiscircuit extending from grounded battery, resistance 6, armature and backcontact of magnet 7 conductor 8, lower armature and back contact ofcut-oit relay 3, oit-normal conducting segment 12, brush 1'1 and thewinding of magnet 7 to ground. Under the influence of this circuitmagnet 7 continues to interrupt its own circuit and advances the lineswitch wipers until an idle trunk is found whereupon the circuitl justtraced will be broken due to the energization of cut-off relay 3. Thetest terminals associa-ted with busy trunks leading to district selectorswitches will be characterized by the absence of potential while thetest terminals kassociated with idle trunks will be characterized byground potential thereon. soon, therefore, as test brush 13 engages theterminal of an idle trunk, a circuit is completed from grounded battery,resistance 6, armature and back contact of magnet 7 (which deenergizedto cause the advance of the switch),arma.ture and front contact of relay2, lower winding of relay 3, test brush 13, Contact 14, conductor 15,left-'hand contacts of sequence switch spring 101, conductor 102,righthand armature and back contact of relay 103, lower right-handcontact of sequence switch spring 104 to ground. Cut-off relay 3 isenergized in this circuit and permanently interrupts the circuit ofstepping magnet 7. Cut-ofi' relay 3 upon energization also opens thecircuit of relay 2 and this relay deenergizes. Relay 3 upon energizationalso completes a. locking circuit for itself extending from groundedbattery, winding of relay 103 (Fig. 2), upper righthand contacts ofsequence switch spring 105, conductor 107, terminal 16 and itsassociated brush 17, innermost upper armature and front cont-act ofrelay 3, upper winding of relay 3 to ground.

Relay 103 is energized in the above-traced circuit and by its right-handarmature removes ground fro-m the test terminal of the trunk selected inorder to render this trunk non-selectable to other hunting lineswitches.

Relay 103 upon energization also completes a circuit extending fromgrounded battery, winding of stepping magnet 108 of the sender selectingswitch. armature and back contact of magnet 108, winding of relay 109,conductor 110, sequence switch spring 169, right-hand armat-ure andfront Contact of relay 103, lower right-hand contact of sequence switchspring 104 to ground. Relay 109 is energized in this circuit andconnects through the various controlling leads to the sender. Theresistance of relay 109 is sufficiently high to prevent the operation ofstepping magnet 108.

rThe sender selector switch is a. step-bysteprotary switch which isadvanced under the control of stepping magnet 108. Magnet 108 maintainsthis switch with its wipers upon the terminals of an idle sender at. alltimes that the district is not in use. The seizure ot' the sender isaccomplished as soon as relay 109 is energized and any sender selectingswitches which are rest-ing on thc terminals associated with the sender,which has just been seized are caused to be advanced by means of acircuit extending from grounded battery, windings of magnets cor--responding to magnet 108, armatures and back contacts of magnets 108`conductors 114, outer left-hand armatures and back co-ntacts of relays109, brushes 113 to the grounded terminal 112. The magnets 108 of senderselectors associated with other districts will then be energized andinterrupt their own circuits to cause the advance of the sender selectorbrushes into engagement with the terminals individual to another sender,and will continue in mo-tion until an idle sender has been found atwhich time they will remain in enga-gement with the terminals of suchsender until it is seized by some district.

Referring to the operation of the circuits shown, the energization ofrelay 109 completes a circuit from grounded battery, winding of relay201 (Fig. upper lefthand contact of sequence switch spring 202,conductor 203, terminal 115 and brush 114 associated therewith, theinner left-hand armature and front contact of relay 109, conductor 116,lower right-hand Contact of sequence switch spring 105, conductor 107,terminal 16, ibrush 17, inne'r upper armature and front contact of relay3, upper winding of relay 3 to ground.

Relay 201 is energized in thls clrcu-it and completes a circuit fromgrounded battery, winding of the power magnet of sequence switch 200,upper right-hand contact of sequence switch spring 257, left-handarmature and front contact of relay 201, to ground, for moving thissequence switch out of position 1 and into position 2. As soon as relay109 operates, the subscribers impulse leads are connected through to theline relay by way of the left-hand armatures of relay 109. The linecircuit toarmature and front contact of relay 109, conductor 131, lowercontact of sequence switch spring 130, conductor 22, terminal 21, brush20 and thence over the loop of the calling su scribers line, returningto brush 19, terminal 18, conductor 129, upper Contact ot' sequenceswitch spring 128, conductorv 127, outer left-hand armature and frontcontact of relay 109, conductor 126, brush 125, terminal 124, conductor217, inner right-hand armature and back contact of relay 215, conductor218, upper right-hand contact of sequence switch spring 219, conductor220, to ground at sequence switch spring 241. Line relay 212 isenergized in this circuit.

With sequence switch 200 in position 2 and with relay 109 energized,circuits are completed for advancing sequence switch 100 out of position1 and into position 2. This is accomplished by energizing relay 117 overa circuit extending Jfrom grounded battery, winding of relay 117, lowercontacts of sequence switch spring 118, conductors 119 and 120, b'rush121, terminal 122, conductor 204, lower left-hand Contact of sequenceswitch spring 205, righ-hand armature and front contact of relay 212 toground. Relay 117 is energized in this circuit and completes a circuitfrom grounded battery, power magnet of sequence switch 100, upperleft-hand contact of sequence switch spring 135, right-hand armature andfront contact of relay 117 to ground, for moving'this sequence switchout of position 1 and into position 2.

1n position 2 of sequenceswitch 100, rela 103 completes a lockingcircuit for it.- self exclusive of the contact of sequence switch spring105. This circuit extends by Way of the left-hand armature and frontcontact of relay 103, the lower contact of sequence switch spring 136,to grounded conductor 107.

As soon as se uence switch 200 reaches position 2, the su sc'riber isfree to dial the characteristic designation of the wanted line in orderto set the registers shown in Fig. It is obvious that the time elapsedbefore'the subscriber is free to dial, is very small, since all that isrequired is that relay 109 operates to cause the operation of relay201,I which moves sequence switch 200 out of position 1 and intoposition 2.

' The selector switches used in establishing the connection are of thetype whose structure and Inode of operation is similar to that of theswitches shown in Patent No. 1,168,319 issued January 18, 1916, to A. E.Lundell. These switches are each of fivehundred-line capacity. In thepresent arrangement, registers are provided which will be set in'accordance with imfpulses transmitted on a decimal basis in accordancewith the digits of the number of the called subscriber. The registerswill then translate these impulses to control the selective operationsof the switches on a nondecimal basis. As shown in the presentdisclosure, provision is made to have a call extended through fourswitches. each of five-hundred lines capacity. In accordance with thewell-known grouping arrangement, by means of the latter two switches ofthe train 10,000 lines may be served. There= Jfore, the rst two switchesof the train will be utilized to select an oliice ot 10,000 lin'ecapacity. The first switch of the train will select a district and thesecond switch of the train will then he operated to select a particularolice. By varying the number of trunk lines in a group at the districtand ollice selector switches, an exchange capacity ranging from4,000,000 to 25,000,000 lines may be obtained. For instance, if eachbrush of the district selector has access to four groups of twenty-fivetrunks each, any one of twenty districts may be selected by the districtselector with twenty-five lines running to each district. If thegrouping arrangement at the oiiice selector is the same, any one oftwenty oiiices may be selected by the oice selector. Therefore.connection may be extended by means of a district selector and an oiiiceselector to any one of four hundred oiiices, each one of 10,000 linecapacity. This would provide a system of 4,000,000 lines. 1f each of thebrushes at the district selector has access to ten groups of trunks often Vlines each, a call may be extended to any one of fifty c listricts.and if the office selector grouping arrangement is the same, the callmay then be further extended to any one of fifty' offices by means of anofiice selector, so that a call may be extended by means of a districtselector and an office selector to any one of twenty-five hundredofiices, each of 10.000 line capacity. As a result, this groupA Ain a-final connector switch. At the final connector switch each of the fivebrushes has access to ten roups of ten lines each, each of these leadingto a subscribers station.

In order that the' calling subscriber may not have to carry in mind alarge number of digits, it is proposed to designate the desired oflicenumber by means of letters of Y the alphabet and three series ofimpulses will be sent to setthree registers to control the first twoswitches of the train. These three registers will control brush andgroup selection at the district selector and brush and group selectionat the office selector. An impulse-sending device of any wellknown typewill be used, being arranged merely lto cause a desired number ofcircuit interruption in response to the operation of a finger wheel. Thesender dial may be lettered .so that in addition to a finger hold` foreach digit, the hold characterized by the No. 0 which would be arrangedto send one impulse, may also bear the letter A. The No. 1 finger holdmay bear the characterizations B and 1. In this way the lettering on the'dial plate complete would be A-0, B-1, C-2, D3,. E-4, F-, G-6, H7,I\-8, J-9.

Under the conditions assumed in the present design of the system, thecode to be dialed for a revertive call would necessitate -an officecharacterization comprising the three letters J-J-J. Since we are atpresent not considering a revertive call, it will be assumed that thecalling subscriber desires to establish connection with a subscriberwhose number is 3456, in an office characterized by the three lettersD-E-F. The subscriber will proceed first to operate his impulse dial tosend four impulses, then to send five impulses, and then to send siximpulses, after which he will proceed to send the digits constitutingthe desired num ber in the selected ofiice..

The registers employed in this system are of the well-known power-driventype and are of a mechanical construction similar to that shown inPatent #1,127,808, issued` February 9, 1915 to Reynolds and Baldwin. Theregister 400, which receives the first letter of the ofhce code willbehereinafter designated as Athe A register' the register 401 will bedesignated as the register and receives the second letter of the officecode; register 402 will be designated the C register and receives thethir letter of the office code. Registers 403, 404, 405 and 406respectivel take up the registrations of the thousan s, hundreds, tensand units digits, respectivel The sequence switch springs shown in igs.5 and 6 are associated with nthe various registers, the springs aboveand below any given register being controlled thereby.

In order that the setting operationv of the registers may be understood,it should be noted that all the register contact springs designated bythe letters B, F and G are so arranged that in the odd positions of theregister switch with which they are associated, the upper contacts willbe closed,

while in the even positions of the switch the lower contacts'will beclosed. In each case the normal position of the switch. will beconsidered as an odd osition.

In response .to the rst series of impulses the circuit of line relay 212is intermittently. interrupted. Upon the first deenergization of relay212 a circuit is completed fram grounded battery, right-hand armatureand back contact of relay 228, conductor 232, upper left-hand contact ofsequence switch spring 235, conductor 236, upper" contacts of sequenceswitch spring 414, which are closed since this is a Gr spring,4conductor 237, left-hand winding of relay 222, lefthand armatureA andback contlact of relay 212, to ground.

Relay 222 is energized in the above traced circuit and completes acircuit from grounded battery, power magnet of register 400, uppercontacts of register spring 412, which is closed-since lthis is a Bspring, conductor 415, upper left-hand contact of se uence switchspringl 238, conductor 239, le -hand armature and front contact of relay222 to ground, for moving this register out of its normal position andinto posi tion 0.

Relay 222, upon energizing, completes two locking circuits for itself byway of its right-hand armature. The first of these extends from groundedbattery, right-hand armature and front contact of relay 222,1eftvhandwinding of relay 222, armature and back contact of relay 212 to ground,and` ino maintainsl this relay energized untilline relay 212 isenergized in response to the completion of the first interruption ofline ductor, 240, upper contacts of register spring 416, which areclosed in the odd position of the register, conductor 417 upperleft-hand contact of sequence switch spring 233, to ground at sequenceswitch sprlng 241. y

The locking circuit through the righthand winding of relay 222 is brokenas soon as register 400 moves into an even Aposition due to the openingof the circuit at the upper contacts of spring 416. When the linecircuit is again completed and relay 212 becomes energized, the circuitthrough the lefthand windlng of relay 222 is broken and the relaydeenergizes.

In response to the next deenergization of relay 212, with the register400 in position 0, a circuit is completed from grounded battery,right-hand armature and back c'ontact of relay 222, conductor 223, upperlefthand contact of sequence switch spring 224, conductor 225, lowercontacts of 'register spring 416, conductor 227 ,left-hand winding ofrelay 228, left-hand armature and back contact of relay 212 to ground.Relay 228 is energized and completes a circuit from grounded battery,power magnet of register 400, lower left-hand contact of register spring412, conductor 413, upper left-hand contact of sequence switch spring229, conductor 230, .left-hand armature and front contact of relay 228to ground, for moving the register out of position 0 and into position1.

Relay 228, upon energization` completes two locking circuits for itselfthrough its right-hand armature, one of these circuits extending fromgrounded battery, righthand armature and front contact of relay 228,right-hand winding of relay 228, conductor 231, lower contacts ofregister spring 414, closed in the even position of the register,conductor, conductor 234, upper lefthand contact of sequence switchspring 233, to ground. The other locking circuit extends from groundedbattery, right-hand armature and Jfront 4contact of relay 228, lefthandwinding of relay 228, left-hand armature and back contact of relay 212,to ground. As before, when the line circuit is again closed, theresultant energization of relay 212 opens the locking circ-uit l throughthe left-hand winding of relay 228,

Vance register 400 out of osition 1 and into position 2 over circuits ientica'l with those circuits previously traced for moving the registerout of its normal position and into position 0. Locking circuits ofrelay 222, identical with those previously described in the descriptionof the operation of this relay, are also completed and interrupted inthe same manner.

In response to the fourth interruption of the line` circuit, relay 228isagain energized to move register 400 from position 2 to position 3,inthe lsame manner as described for moving it from position 0 toposition 1, the cycle of ope-ration of relay 228 in this case fbeing thesame as when it was previously' brought into use.

It will thus be seen that for each interruption of the line circuit theregister 400 will be advanced one position. At the termination of thefirst series of impulses, at which time four interruptions of the linecircuit will have occurred, the register 400 will have advanced foursteps into position 3. Relay 228 is energized in response to the lastdeenergization of linel relay 212.

It is to be observed that as soon as register 400 left its normalposition, a circuit was completed for relay 242 (Fig. 3), this circuitextending from grounded battery, winding of relay 242, lower contact ofsequence switch spring 243, conductor 244,/ upper4 right-hand contact ofsequence switch spring 418, lower contacts of register springs 419, 420,421, 422, 423, and 424 in series, conductor 425, left-hand armature andfront contact of relay 212 to ground. This circuit is completedmomentarily each time relay 212 is energized during the sending of thefirst series of impulses. Relay 242 is, however, designed to be slow toattract its armature and, therefore, these momentary circuit closureswill not allow its armature to close its contact. However, afterregister 400 has been positioned and during the interval between thesending of the iirst and second. series of impulses, relay 212 remainsenergized Jfor a relatively long time and as a result, relay 242attracts its armature, thus completing a circuit from grounded-battery,power magnet of sequence switch 200, upper right-hand contact ofsequence switch spring 245, conductor 246 to ground, for'moving thissequence switch out of position 2 and into position 3. When sequenceswitch 200 leaves position 2, the energizing circuit of relay 242 isbroken at the lower contact of sequence switch spring 243, and relay 242deenergized. i

In position 3 of sequence switch 200 the second series of impulses maybe received. Five impulses will be sent to advance register 401 livesteps into position 4. At this time, relays 222 and 228 function tocontrol the advance of register 401 in a manner substantially similar tothat previously described. At this time, however, the energizing circuitfor relay 222 extends through thev upper right-hand contact ot' sequenceswitch spring 235, conductor 247, upper contacts of register spring 426,conductor 237, and thence to ground as previously described. Theenergizing circuit of relay 228 extends by way of the upper right-handcontact of sequence switch spring 224, the lo-wer contacts of registerspring 427 and conductor 227, to ground as previously described. Theoperation of setting register 401 41s fundamentally similar to that otsetting register 400 and it is thought need not be described in detail.

After the second series of impulses has been sent, relay 212 will remainenergized a comparatively long time and will complete a circuit forrelay 242 from grounded battery, winding of relay 242, upper contact ofsequence switch spring 243, conductor 248, upper contact of registerspring 419, and thence through the lower contacts of register springs420, 421, 422, 423 and 424 in series, and conductor 425 to ground asdescribed. This circuit has beeny intermittently closed upon each shortactuation of relay 212 but does not become effective until after thesending of the series df impulses. When re lay 242 is energized, acircuitis completed from grounded battery, power magnet of sequenceswitch 200, upper right-hand contact of sequence switch spring 245,conductor 246, armature and front contact of relay 242, to ground formoving this sequence switch out of position 3 and into position 4.

The subscriber continues sending series of impulses, and as a resultregister 402 will 'be set in position 5, register 403 will be set inposition 3, register 404 will be set in position 4, register 405 will beset in position 5, and register 406 will be set in position 6.

Upon the completion of the setting of register 402, the energization ofrelay 242 will advance sequence switch 200 from position 4 to position5, the completion of the setting of register 403 will advance sequenceswitch 200 into position 6; the completion of the setting of register404 will advance sequence switch 200 into position 7; the completion ofthe setting of register 405 will advance sequence switch 200 in position3, and when the last register 406 is positioned, sequence switch 200will be advanced out of position 8 and into position 9.

Vhen sequence switch 200 reaches position 4, at which time registers 400and 401 will have been positioned, these being the regis` ters whichcontrol the district selector switch shown in Fig. 2` a circuit iscomple-ted from grounded battery, power magnet of sequence switch 300(Fig. 7), lower right-hand contact of-sequence switch spring 301,conductor 302,

contact of sequence switch spring 249 to ground, for moving thissequence switch out ofnosition 1 and into position 2.

n position2 of sequence switch 300 the fundamental circuit is completedto control selection at the district switch. A circuit is completed fromgrounded battery, winding of relay 117 (Fig. 2) upper contacts otsequence switch spring 118, conductors 137 and 138, brush 139, terminal140, conductor 250, armature and back contact of relay 304,

Iwhich is in parallel with the 0 cqunting relay, winding of steppingmagnet`305, upper contact of sequence switch spring 306, conductor 307,through the contactsof register springs 428 and 429 in parallel,conductor 430, lower right-hand Contact of sequence switch spring 205,conductor 204, terminal- 122, brush 121, conductor 120, upper righthandand lower left-hand contacts of sequence switch spring 141, resistance142 to ground. Relay 117 is energized in this circuit and locks up toconductor 137 through its lett-handarmature and front contact.

It is to be observed that, if both registers 400 and 401 are in position9, which corresponds to the sender designation J, the fundamentalcircuit would not havebeen completed, since both register springs 428and 429 would have been open. It is therefore obvious that in case therevertive ringing. oice code has been sent, which comprises the lettersJJJ, the relay 117 would not have been energized and would not haveadvanced the district as will now be described. The

operation of the system in connection with aarmature and back contact ofthe No. 2

counting relay, conductors 308 and 431, lower left-hand contact ofsequence switch spring 432, conductor 433, upper left-hand contact ofsequence switch spring 309, conductor 310 to ground at the armature andfront contact ot' stepping relay 305. The No. 2 counting relay isenergized inythis circuit and preparesa circuit Jfor the No. 2 countingrelay which does not become effective until the stepping relay isdeenergized to remove the shunt about the winding ot f:

the No. 2 counting relay.

In position 3 of sequence switch 100, a circuit iscompleted fromgrounded battery, winding of up-drive magnet 143, right-hand contacts ofsequence switch springs 144,

right-hand armature and front Contact of relay 117 to ground. Magnet 143is energized and causes the brush shaft to be moved upward in a brushselecting movement. As Soon as commutator brush 152 engages a conductingsegment of commutator 146 the holding circuit of relay 117 is extendeddirectly to ground at the district selector, this circuit extending fromgrounded battery, winding of relay 117, left-hand armature and frontcontact of relay 117, upper lefthand Contact of sequence switch spring118, upper left-hand contact of sequence switch spring 147 conductor148, commutator 146 and brush 152 to ground. Stepping relay 305 isshunted down in this circuit and allows the No. 2 counting relay tobecome energized. When brush 152 engages an insulating segmentofcommutator 146, relay 305 again becomes energized and causes theenergization of the No. 1 counting relay. Stepping relay -305 isintermittently actuated as the brush shaft moves upwardly until, on itsthird deenergization, the 0 counting relay and relay 304 are energized.Relay 304 opens the lower.branch of the loc-kino' circuit of relay 117and when, a moment ater, brush 152 engages an insulating portion ofcommutator 14 at which time the brush shaft will be properly positionedto trip the third set of brushes, the locking circuit for rela-y 117 iscompletely broken and this relay deenergizes and opens the circuit ofthe up-drive magnet, thus bringing the brush shaft to rest. Thedeenergization of relay 117 also completes a circuit from groundedbattery, power magnet of sequence switch 100, lower right-hand contactof sequence switch spring 135, right-hand armature and back contact ofrelay 1,17, to ground, for moving this sequence switch out of position 3and into position 4.

In the sender, the energization of the 0 counting relay completes acircuit from grounded battery, power magnet of sequence switch 300,upper left-hand contact of sequence switch spring 301, armature andfront contact of the 0 counting relay to ground, for moving this switchout of position 2 and into position 3. Since relay 290 (Fig. 3) is notenergized at this time, due to conditions which will be subsequentlydescribed, sequence switch 300 is immediately moved out of position 3and into position 4, due to the completion of a circuit extending fromgrounded battery, power magnet of sequence switch 300, lower left-handcontact of sequence switch spring 311, conductor 312, armature and backcontact of relay 290 to ground.

With sequence switch 100 in position 4 and sequence switch 300 inposition 4, the fundamental circuit is again completed to advancesequence switch 100 out of position 4 and into position 5 by means ofcircuits identical with. those previously traced for moving thissequence switch out of position 2 and into position 3. v 4

In position 5 of sequence switch 100Atl1e district brush shaft is movedupward in a group selecting movement due to'the closure of a circuitfrom grounded battery, winding of up-drive magnet 143, left-handcontacts of sequence switch spring 144, right-hand armature and frontcontact of relay 117 to ground. It is to be observed that as soon assequence switch 100 reaches position 4, a circuit is completed fromgrounded battery, winding of trip magnet 149, Contact of sequence switchspring 150, lower left-hand" contact of sequence switch spring 151 toground. The resultant energization of magnet 149 operates the trip rod180 so that upon subsequent upward movement of the brush shaft the thirdset of brushes will be released into engagement with the terminalsserved by them.- i

TheA first energization of stepping relay 305 completes a circuit fromgrounded battery, winding of the No. 2 counting relay, armature and backcontact of the No. 2 counting relay, conductors 308 and 434, lowerleft-hand contact of sequence switch spring 435, upper contact ofsequence switch spring 436, conductor 437, upper right-hand contact ofsequence switch spring 309, conductor 310, armature and front contact ofrelay 305 to ground. Stepping relay 305 is intermittently shunted downas the brush moves upwardly due to the engagement of commutator brush152 with commutator 153 which supplies holding ground directly to relay117 by way of the upper left-hand contact of sequence switch spring 147and conductor 148. Upon the third shuntingv down of the stepping relaythe 0 counting relay and relay 304 are energized in parallel. Relay 304permanently opens the lower branch of the locking circuit of relay 117and when, a moment later, the brush 152 engages an i11- sulating segmentof commutator 153, relay 117 deenergizes and completes a circuit fromgrounded battery, lower' right-hand contact of sequence switch 135,right-hand armature and back contact of relay 117 to ground for movingthis switch out of position 5 and into position 6. The deenergization ofrelay 117 opens the circuit of up-drive magnet 143, and brings the brushshaft to rest with the selected set of brushes in operative relation tothe selected group of trunk lines.

In the sender, the energization of the 0 counting relay completes acircuitl from grounded battery, winding of the power magnet of sequenceswitch 300, upper lefthand contact of sequence switch spring 301,armature and front contact of the 0 count-l -ing relay to ground, formoving this seout of position 5 and into position 6 due to the closureof a circuit for its power magnet extending from the lower left-handcontact of sequence switch spring 311 by way of conductor 312 to groundat the armature and back contact of relay 290.

In position 6 of sequence switch 100, a circuit is completed 4fromgrounded battery, left-hand winding of test relay 155, lower right-handcontact of sequence switch spring 156, conductor 157 to ground, at therighthand armature and back contact ot relay 117. Relay 155 is energizedin this circuit and locks up through its right-hand winding over acircuit extending from grounded battery, right-hand winding of relay155, up-

per contacts of sequence switch spring 158, right-hand armatureand'front Contact of relay 155, conductor 160, test'brush 159 and itsassociated terminal 161 to ground, provided that the first trunk in theselected group is busy, it being understood that busy trunks will becharacterizedby the presence of ground potential on their testterminals, while no potential will be found on the terminals of idletrunks.

Relay 155 upon energization also completes a circuit from groundedbattery, power magnet of sequence switch 100, upper left-hand contact ofsequence switch spring 135, left-hand armature and front contact ofrelay 155 to ground, for moving this sequencet switch out of position 6and into position 7.

In position 7 of sequence switch 100 the selected set of brushes ismoved upward in a trunk selecting movement due to the closure of acircuit from grounded battery, winding of up-drive magnet 143,right-hand contacts of sequence switch spring 144, left-hand armatureand front contact of relay 155 to ground.

As soon as test brush 159 encounters the terminal of an idle trunk thelocking circuit through the right-hand winding of relay 155 is opened.Relay 155 does not immediately deenergize, however, dgue .to theexistence of a circuit from grounded battery, left-hand windin of relay155, upper right-hand contact o sequence switch spring 156, conductor162, commutator 163, commutator brush 176 to ground. When, an instantlater, brush 176 engages an insulating segment of commutator 163, atwhich time the brush set will be accurately centered on the terminals ofthe selected trunk, relay 155 deenergizes and opensr 'the circuit ofup-drive magnet 143 to bring the selected brush set to rest on theterminals of an idle trunk leading to the oiice selector. Thedeenergization of relay 155 also completes a circuit from groundedbattery, power magnet of sequence switch 100, upper lefthand contact ofsequence switch spring 165,

left-hand armature and back contact of relay 155 to ground, for movin"this switch out of position 7 and into position 10. 1

The fundamental circuit is now completed from grounded 'battery at theoffice selector associated with the seized trunk, over conductor 166,terminal 167, brush 168, upper contact ot' sequence switch spring 169,conductor 138, brush 139, terminal 140, conductor 250, armature and backcontact of relay 304, winding of stepping relay 305, upper contact ofsequence switch spring 306, through the upper contacts of registersprings 428 and 429 in parallel, conductor 430, lower right-hand Contactof sequence switch spring 205, conductor 204, terminal 122, brush 121,conductor 120, upper contact of sequence switch spring 170, brush 171,terminal 172, conductor 173, to ground at the oilice selector throughthe usual switching devices at the oiiice selector. The updrive magnetat the office selector Vis then brought into service and brush selectiontakes place in substantially the same manner as described in connectionwith the district selector. The office selector in this movement willcause interruptions of the flow of current to the stepping relay 305 bymeans of an interrupting commutator corresponding to commutator 146 andbrush 152 at the district selector.

The closure of the fundamental circuit causes the energization of relay305. Upon the energization of stepping relay 305 a circuit is completedfrom ground, armature and front contact of relay 305, conductor 310,lower right-hand Contact of sequence switch spring 309, conductor 313,contact of register spring 438, upper contact of register spring 439,upper left-hand contact of register s-pring 440, conductors 441 and 308,

armature and back contact of the No. 2V

counting relay, andthe winding of the No. 2 counting relay to groundedbattery. The No. 2 counting relay prepares a circuit for the No. 2counting relay in the well known manner. The movement of the ofceselector operates the counting relays until the 0 counting relay andrelay 304 are energized. Relay 304 opens the fundamental circuit, thusopening one branch of the circuit of the relay which controls the otiiceselector and causing the subsequent stopping of the office selector in aposition to trip the third set of brushes.

The energization of the 0' counting relay closes a circuit from groundedbattery, power magnet of sequence switch 300, upper lett-hand contact ofsequence switch spring 301, armature and front contact of 0 countingrelay to ground, for moving this sequence switch out of position 6 andinto position 8. In passing from position 6 'to position 8, the holdingcircuits of the counting relays are opened at sequence switch springs314 and 315 and the counting relays are deenergized.

In position 8 of sequence switch 300, the fundamental circuit is againclosed 'through to the office selector and again causes the energizationot' the up-drive magnet at the oflice selector. Groupl selection willnow take place. As the switch shaft, is elevated relay 305 is againintermittently shunted by means of a circuit Jfrom a colrunutatorsimilar to coinmutator 153 at the district selector. The firstenergization of stepping relay 305 completes a circuit from ground,arma-ture and Jfront contact of relay 305, conductor 310. lowerleft-hand contact of sequence switch spring 309, conductor 314, contactof register spring 442, upper 'contact of register spring 443, upperleft-hand contact of register' spring 444, conductors 445, and 446,armature and back Contact of No. 5 counting relay and the Winding ofthe'No. 5 counting relay to grounded battery.

As the ofiice selector switch moves upward in the group selectingmovement the counting relays will be successively actuated in the samemanner as above described. As soon as relay 304 is energized theJrundamental circuit is opened, thus stopping the selected set ofbrushes of the oflice selector at the bottom of the fourth group ofterminals served thereby. The energization of the 0 counting relaycompletes the above traced circuit for moving sequence switch 300 out ofposition 8 and into position 10.

Meanwhile trunk hunting takes place at the ofiice selector in a mannersubstantially like that described in connection with the districtswitch, and upon completion of trunk hunting, the ofiice selector willhave seized a set of terminals leading to an idle incoming switch in thedesired oflice.

Since the operation of the incoming and final switches are well known inthe art. it is not believed to be necessary to describe the operation ofthe sender in connection with the setting of these switches. Inpositions 10 and 12 of sequence switch 300, brush selection and groupselection, respectively, at the incoming switch will be controlled. Theincoming switch will then trunk hunt to pick anidle final switch,whereupon the fundamental circuit will be again completed and inposition 14 of sequence switch 300, final brush selection will beaccomplished. In position 16 of sequence switch 300, group selection ofthe final will take place. and in position 17 of sequence switch 300final line selection will take place. The called line will be tested andif idle will be signaled in the well known manner.

Since the number of the line wanted was 3 4 5 6, the second brush andthird group of the incoming switch will-have been selected, and at thefinal, the fifth brush, sixth v the final switch, the energization ofthe 0 counting relay operates to advance sequence switch 300 out ofposition 17 and into position 18, in the usual manner. y,

As soon as sequence switch' 30.0 reaches position 18, a circuit is.completed from .grounded battery, power magnet of sesol quence switch200, Fig. 3, upper right contact of sequence switch spring 251,conductors 253 and 254, closed contacts of reg-` ister spring 447,conductor 448, upper righthand contact of sequence switch spring 351 toground, for moving sequence switch 200 out of position 9 and intoposition 13.

In position 13 of sequence switch 200, a circuit is completed fromgrounded battery, left-hand winding of relay 155, (Fig. 2) lowerleft-hand contact of sequenceswitch spring 156, conductor 176, brush177, ter# minal 178, conductor 255, lower4 left-hand" contact 'ofsequence switch spring 256 to. ground. Relay 155 is energized in thiscirf cuit and completes a circuit from grounded battery, power magnet ofsequence'switch 100, upper left-hand contact of sequence switch spring135, left-hand armature and front contact of relay 155=to ground, formoving this sequence switch out of position 10 and into position 14. Itis to be ob# served that relay 155 upon energization locks up throughits right-hand winding and the upper contacts of sequence switch spring158-, the left-hand 'armature and front contact of relay 155 and theupper right-hand and lowerleft-hand contacts of sequence switch spring104, until sequence switch 100 leaves position 13'. Relay 155 is thendeenergized and allows the sequence switch to come to rest in position14.

As soon as sequence switch 100 leaves position 134, the impulse leadsinto the sender 'are opened at sequence switch springs 128 and 130, andline relay 212 is allowed to deenergize. At the same time the circuitlof relay 109 is opened at sequence switch sequence switch springs 128and 130 respectively. Current flow over the subscribers line causes theenergization of relay 181 which becomes energized and causes in turn theenergization or' relay 182 over a circuit extending Jfrom groundedbattery, winding of relay 182, armature and front contact of relay 181,right-hand armature and front contact of relay 103 to ground, at thelower lefthand contactot sequence switch spring 104. The energiz'ationof relay 182 completes a circuit from grounded battery, power magnet ofsequence switclr 100, lower left-hand contact ot sequence switch spring135, armature and front contact of relay 182 to ground, for moving thissequence switch out of position 14 and into position 15.

Referring now to the register controlling circuit shown in Fig. 3, itwill be noted that when sequence switch 100 left position 11, the upperbranch of the locking circuit of relay 201 was broken at sequence switchSpring 105, and when sequence switch 100 leaves position 13% to causethe deenergization of relay 109, the subsequent deenergization of linerelay 212 opens the lower branch of the locking circuit of relay 201.Relay 201 thereupon deenergizes and completes a circuit from groundedbattery, power magnet of sequence switch 200, upper left-hand contact ofsequence switch spring 257, left-hand armature and back contact of relay201 to ground, for moving this sequence switch out of position 13 andinto position 15.

In position 15 of sequence switch 200, the various registers shown inFig. 5 are restored. The first register to be restored is register 406,by means of a circuit extending from grounded battery, power magnet ofregister 406, upper right-hand contact of register spring 449, conductor450, lower left-hand contact of sequence switch spring 219, conductor220 to ground at sequence switch spring 241. Register 406 rotates untilit reaches its normal position at which time the driving circuit justtraced will be opened at the upper contact of register spring 449. Assoon as register 406 reaches its normal position, a circuit is completedfor restoring register 405, extending from grounded battery, powermagnet of register 405, upper contact of register spring 451, lowerleft-hand contact of register spring 449, conductor 450 to ground overthe path described. Register 405 is then advanced into its normalposition where it is brought to rest and at the same time completes thecircuit for restoring register 404. In this manner the restoration ofthe registers continues until all the registers have returned to theirnormal position whereupon a circuit is completed from grounded battery,power magnet of sequence switch 200, upper left-hand Contact of Sequenceswitch spring 251, conductor 258 and thence through register springs452, 453, 454, 455, 456, 451 and 449 respectively, as soon as the. lowercontacts of these register springs are closed in the normal positions ofthe registers, and thence to ground over conductor 450 over the pathdescribed. The completion of this circuit advances sequence switch 200out of position 15 and into position 18.

As soon as sequence switch 20() reaches position 18, a circuit iscompleted from grounded battery, power magnet of sequence switch 300,upper lett-hand contact of se quence switch spring 811, conductor 316,upper right-hand contact of sequence switch spring 259, conducto-r 220to ground at sequence switch spring 241. Completion of this circuitadvances sequence switch 300 out of position 18 and into position 1.

lVhen sequence switch 300 reaches position 1, a circuit is completedfrom grounded battery, power magnet of sequence switch 200, lowerright-hand contact of sequence switch spring 251, conductor 260, lowerright-hand contact of sequence switch spring 351 to ground, for movingthis sequence switch out of position 18 and into position 1. The variousregisters, the sender and the register controlling equipment have nowall been restored to their normal condition and are ready for reuse. Itis to be noted that after relay 109 releases and removes from its'outerleft-hand armature the ground which was maintaining the sender busy, thesender is protected against seizure until it is fully restored bymeansbf ground supplied to test terminal 112, from sequence switchspring 241, Fig. 4, by way of conductor 220, the upper left-hand Contactof sequence switch spring 259 Iand conductor 261. W hen sequence switch200 reaches position 1, this ground is removed and the sender may againbe selected for reuse.

Conversation takes place in position 15 of sequence switch 100. Uponcomplet-ion of the conversation the calling subscriber re places hisreceiver upon the switchhook, thus opening the line circuit. Relay 181deenergizes and causes the release of slow release relay 182. Relay 182upon deenergization completes a circuit from grounded battery, powermagnet of sequence switch 100, lower left-hand contact of sequenceswitch spring 165, armature and back con tact of relay 182 to ground formoving this sequence switch out of position 15 and into position 18. i

In position 18 of sequence switch 100, a circuit is completed fromgrounded battery, winding of'down-drive magnet 173, and the lowercontacts of sequence switch spring 151 to ground. Magnet 173 isenergized and causes the restoration of the district selector. When thebrush shaft is fully returned to its normal position, a circuit iscompleted from grounded battery, winding of power magnet of sequenceswitch 100, lower contact of sequence switch spring 174, commutatorsegment 175, brush 176 to ground, for moving sequence switch 100 out otposition 18 and into position 1.

As soon as the district selector brushes 168, 171 and 159 leave theterminals of the trunk leading to the office selector, restoration ofthe oflice selector is started. The oiice selector, incoming, and finalswitches are restored in the usual manner.

When the sequence switch 100 leaves position 18, the holding circuit ofthe cut-off relay 3 is broken and this relay deenergizes and causes therestoration of the subscribers individual line switch, by completing acircuit from grounded battery, resistance 6, armature and back contactof stepping magnet 7, conductor 8, lower armature and back contact ofcut-oit' relay 3, off normal segment 12, brush 11 and the winding ofstepping magnet 7 to ground. Stepping magnet 7 interrupts its owncircuit and cont-inues to do so until the switch has been advancedthrough a complete revolution and back to its normal position, at whichtime brush 11 will leave segment 12 and permanently open the circuit ofmagnet 7. During the return of the switch, the wipers will pass overbusy and idle trunks without stopping, since line relay 2 is notenergized at this time. All ot the apparatus has now been restored toits normal condition and is ready for reuse.

The conditions which arise in case the calling subscriber abandons thecall, either before dialing to set any of the registers or after he hasdialed to set some of the registers but not all of them will now bedescribed.

It will first be assumed that a subscriber abandons the call withoutoperating his dial at all. In this case his initial removal of thereceiver will cause his line switch to pick an idle district aspreviously described. 'preselected sender will then be connected to thedistrict and advanced into position 2 as described. The districtsequence switch will also be advanced into position 2. Assuming now thatthe calling subscriber replaces his receiver at this time, line relay212 willbe deenergized and will cause register 400 to be advanced onestep into its 0 position. Line relay 212 will now remain deenergized andwill allow relay 262 to become energized over a circuit extending fromgrounded baittery, winding of relay 262, lower contact of sequenceswitch spring 263, right-hand armature and back contact of relay 212 toground. This circuit is normally completed upon each interruption of theline circuit during the sending of the series of impulses. Relay 262 ishowever designed so as to be slow to attract its armature and thereforedoes not become energized during the normal operation of the system. Incase of an abandoned call however, relay 262 becomes deenengized4 andcompletes a circuit from grounded battery, power magnet of seguenceswitch 200, upper lefbhand contact o sequence switch spring 245, arma'-ture and front contact of relay 262 to ground, for moving this sequenceswitch out of position 2 and into'position 9. Since only one of theregisters has been advanced out of its normal position, a circuit isthen.

at once effective to advance sequence switch 20() out of position 9 andinto position 13. This circuit extends from grounded battery, powermagnet of sequence switch 200, lower left-hand contact of sequenceswitch spring 251, conductor 252 through the lower contacts of registersprings 457, 458, 459, 460, 461 and 462 in parallel to ground. Sincesequence swich 200 does not come to rest in position 4 at this time, butpasses directly through it, sequence switch 300 is not moved out ofposition 1, since ground is closed to lead 302 for an insufficientperiod of time to allow this sequence switch to advance.

When sequence switch 200 reaches position 13, a circuit is completedfrom grounded battery, winding of relay 117, Fig, 2, lower right-handand upper left-hand contacts of sequence switch spring 118, conductors137 and 138, brush 139, terminal 140, conductor 250, right-hand contactof sequence switch spring 256 to ground. Relay 117 is energlzed in thiscircuit and completes a circuit from grounded battery, power magnet ofsequence switch 100, upper left-hand contact of sequence switch spring135, right-hand armature and front contact of relay 117 to ground, formoving this sequence switch out of position 2 and into position 3. Sincesequence switch 200 is in position 13, sequence switch 100 isimmediately moved out of position 3 and into position 4 by means of acircuit extending from grounded battery, power magnet of sequence switch100, lower right-hand contact of sequence switch spring 135, contact ofsequence switch spring 183, conductor 176, brush177` terminal 178,conductor 255, lower left-hand Contact of sequence switch spring`256 toground, When sequence switch 100 lreaches position 4, since the districtselector has not been put into operation, a circuit is completed. fromgrounded battery, power magnet of sequence switch 1 00, contact ofsequence .switch spring -=174, v'noirmall commutator 4segment 175 andbrush 176 to ground, for moving this sequence switch out of position 4and into. position 15. Since the call was abandoned, relay 182 will nothave been energized and therefore a circuit it at once completed fromgrounded battery. power magnet l"of sequence switch 100, lower lefthandContact of sequence switch spring 165, armature and back contact ofrelay 182 to ground, for moving sequence switch 10() out of position 15and into position 18 from which position it is at once moved into 1 bymeans of the previously traced circuit eX- tendingthrough the contact ofsequence switch spring 174- and normal commutator segment 175 and itsassociated commutator brush 176 to ground. y

The release of the district selector causes the release of relay 201,Fig. 3, which advances sequence switch 200 out of position 13 and intoposition 15, wherein register 400 is restored to its normal position.With all the registers in their normal positions, circuits identicalwith those previously traced are completed to advance sequence switch200 into position 18, from which position itis advanced into position 1as previously described. l

If the subscriber abandons the call after withoiit completing the fullregistration, the restoration of the registers and various controllingapparatus is substantially similar. In case the first three registershave been set, the fundamental circuit will have been completed and thevarious selective operations will have been started at the time the callis abandoned. The continued deenergization of relay 212 at this timewill cause the energization or" relay 262 and sequence switch 200 willbe advanced into position 9 as previously described. Since some one, orperhaps several, of the registers are in their normal positions at thetime sequence switch 200 reaches position 9, a circuit will again becompleted for advancing sequence switch 200 by way of the lowerleft-hand contact of sequence switch spring 251 and conductor 252.

Meanwhile the district switch will complete its selective operations andsequence switch 100 will come to rest in position 10, A circuit is thencompleted from grounded battery, left-hand winding of relay 155, lowerleft-hand contact of sequence switch spring 156, conductor 176, brush177, terminal 178, conductor 255, lower left-hand contact of sequenceswitch spring 256 to ground. Relay 155 is energized and at its left-handarmature and front contact completes a circuit for moving sequenceswitch 100 out of position 10 and into position 14.

A circuit is then completed Jfrom grounded battery, winding ofdown-drive magnet 17 3, lower contacts of sequence switch spring 151 toground. Magnet 17 3 is energized and causes the restoration of thedistrict selector brush shaft. When the district brush shaft reaches itsnormal position sequence switch 100 is advanced out of position 1 4 andinto position 15, and thence into position 1 as previously described inconnection with an abandoned call.

.As soon as the district selector brush set dialing a number of seriesof impulses, but.

leaves the terminals of the trunk leading to the oiiice selector, theincoming selector and any succeeding switches in the train are releasedin the well known manner.` Under the conditions assumed, sequence switch20() is advanced into position 18 as previously described whereupon acircuit is completed Jfrom grounded battery, power magnet of sequenceswitch 300, upper left-hand contact ofV sequence switch spring 311,conductor 316, upper right-hand contact of sequence switch spring 259,conductor 220 to ground at sequence switch spr-ing 241. The completionofthis circuit advances the-sender sequence switch 300 out of whateverposition it happens to be in, into position 1, whereupon sequence switch200 is advanced out of position 1S and into position 1. The apparats isnow all in its normal condition.

The operation of the system when used by a subscriber on a party line inmaking a revertive call to a stationon the same line will now bedescribed.

The invention has been shown applied to a system in which revertiveringing may be accomplished on a fourpart line of the type in which adesired one o the four stations may .be selectively rung by applyingringing current superimposed on lplus or minus battery to either the tipor the ring side of the line. Since the systemcould easily be adapted tooperate with any type of party line ringing system, whether ar-.

ranged for two or four party lines, it is not to be restricted to thespecific embodiment shown, which merely illustrates one form of carryingout the principles involved.

As previously stated any party line sub` scriber in the system,regardless of which oiiice he is in will dial a characteristic officecode when he desires to make a revertive call. To accomplish this, eachparty line subscribed will be supplied with the names of the subscriberswho are on his own party 1 line, since these numbers will have norelation to the numbers appearing in the regular directory. Thedirectory numbers will, of course, be used by any other subscribers whodesire to converse with a subscriber on a given party line, providedthat they are not on the same line.

As just stated by first dialing impulses corresponding to the lettersJJJ the sender registers will be set in positions to accomplishrevertive ringing. The thousands, hundreds, tens and units registerswill then be positioned and determine which substa tion on the partyline will be rung.

Briefly the general operation is as follows: The subscriber initiating acall will dial JJJ and then dial the number which corresponds to theparticular party line station on his own line which he desires tosignal. He will then replace his receiver I on the switch-hook. Thesender vand special revertive ringing apparatus will then be operated toring first the called subscribers station and then the station of theoriginating subscriber. The ringing of the bell at the originatingsubscribers station informs him that the system is operatingsatisfactorily and that the called subscriber has not yet answered. Whenthe called subscriber removes his receiver from the switchhook ringingcurrent is disconnected, and the bell at the originating station ceasesto ring, thus informing the calling subscriber -that\ the called partyhas answered. He will then remove his receiver from the switchhook andmay converse with the called subscriber.

- Battery for "the conversation is supplied out of its normal position.

from the district switch which is held byy `the calling subscribers lineswitch. The

district switch, however, does not advance Referring now to Fig. 6,thousands register spring 464, hundreds register springs 466 and 467,tens register spring 469 and units register springs 471 and 472 are thespringswhich determine which two parties shall be signaled in the caseof a revertive call. In the case of all of these four registers thedigits 2 and 1 are the only ones which are used to control the ringingselections.

It will be assumed that the subscriber whose substation is signaled byringing current superimposed on plus battery applied to the ring side ofthe line desires to talk with a subscriber on the same party line whosesubstation may be signaled by ringing current superimposed on minusbattery applied to the tip side of the line. He will consult hisindividual card showing the substations on his own party line and willlearn that the number he must dial is J J J 1221.

The. calling subscriber thereupon removes his receiver from theswitchhook and his individual line switch selects anidle trunk to adistrict switch in a manner identical with that described in connectionwith a non-revertive call. He will then dial J J J 1221 to set the Aregister in position 9, the B register in position 9, the C register inposition 9, the thousands register in position 1 the hundreds registerin position 2, the tens register in positionv 2 and the units registerin position 1. The operation of the district circuits and the registercontrolling circuits in Fig. 3 is identical with that previouslydescribed and it is thought that no further description is necessary.

After the registers have all been set the district sequence switch 100will be in position v2, the register controlling sequence switch 20,0will be in'position 9 and the sender sequence switch 300 4will have beenIt is to be observed that when sequence switch 200 reaches position 4,however, the fundamental circuit including 'line relay 117 (Fig. 2) isnot completed. This circuit extends from grounded battery, windin ofrelay 117, lower right-hand and upper i hand contacts of sequence switchspring 118, conductors 137 and 138, brush 139, terminal 140, conductor250, armature and back contact of'relay 304, winding of stepping relay305, contact of sequence switch spring 306, conductor 307 to registersprings 428 and 429 inl parallel. `Since the A and B registers'are bothin position y9', in the case of a revertive call, springs 428 and 429are both openand the fundamental circuit is not completed to startselection at the district switch. The district sequence switch there- 2,the shunt path about relay 290 is reino-ved, since this shunt is nowopen at each of the register springs 411,472, 473, 463, 465, 468 and 470, at any one of which it would normally be in existence provided anydesignation other than JJ J had first been dialed or 1n case' any one ofthe numerical registers has not been advanced beyond its zero position.The relay 290 is now included in the line circuit which extends fromgrounded battery, winding of relay 212, winding of relay 290, conductors263 and 214 left-hand armature a-nd back contact of relay 215, conductor216 'and thence through the calling substation to ground as previouslydescribed.

Relay 290 responds in series with line relay 212 since the line circuitis closed immediately following the termination of the last series ofimpulses. Relay 290 upon energization completes a circuit .from groundedbattery, power magnet of sequence switch 300, left-hand contacts ofsequence switch spring 320, conductor 321, armature and frontv contactof relay 29() to ground, for moving sequence switch 300 out of position2 and into position 3.

The calling subscriber will then replace his receiver and await theringing of the called subscriber. The resultant` interruption of theline circuit allows relays 212 and 290 to be deenergized. Thedeenergization of relay 290 completes a circuit from grounded battery,power magnet of sequence switch 300, lower left-hand contact -ofsequence switch sp-ring 311, conductor

